Epidemiology

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• Epidemiology
• of
• Typhoid fever

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• Typhos in Greek means ,smoke and typhus fever got
  its name from smoke that was believed to cause
  it. Typhoid means typhus-like and thus the name
  given to this disease.
• The term Typhoid was given by Louis 1829 to
  distinguish it from typhus fever.
• It is a disease of poor environmental sanitation
  and hence occurs in parts of the world where
  water supply is unsafe and sanitation is
  substandard.

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• In 1880s, the typhoid bacillus was first
  discovered by Eberth in spleen sections and
  mesenteric lymph nodes from a patient who died
  from typhoid.
• Robert Koch confirmed a related finding and
  succeeded in cultivating the bacterium in 1881.
• Serodiagnosis of typhoid was thus made possible
  by 1896.
• Wright and his team prepared heat killed vaccine
  from S.Typhi in 1896

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• Disease caused by Salmonellae typhi.
• Non-spore-forming. gram ve rods, aerobic,
  motile with flagella,
• Salmonella currently comprise 2000 serotypes
• Two groups a) Enteric fever group
• b) Food poisoning group
• The proportion of typhoid to paratyphoid A is
  101.

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• The bacilli are killed at 55ºc in one hour or at
  60ºc in 15 minutes.
• They are killed within 5 minutes by mercuric
  chloride or 5 phenol.
• Boiling or chlorination of water and
  pasteurization of milk destroy the bacilli

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• In past, many deaths were due to typhoid fever
  worldwide.
• Now mostly
• localized to developing countries.
• People are not only become ill and die but can
  become colonized by S. typhi resulting in being
  carriers and spread typhoid fever.

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• An acute infection with prolonged fever due to
  Salmonella typhi sometimes lead to severe
  complications.
• Globally 16 million cases with 600000 deaths
  annually.
• Salmonella paratyphi A B lead to milder
  disease.
• Peak age 4-19 years.

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Typhoid Fever
Ingest S. typhi
Bacteria invades intestinal cells and
translocates to systemic organs
Multiplies to high number in liver and spleen
Spreads to bloodstream
Bacteria move to gallbladder
Bacteria persists in gallbladder
Shed in Bile
Bacteria shed in feces
DEATH
TYPHOID
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Poorer Countries are Vulnerable

• Typhoid Fever seems to matriculate in places with
  poor sanitary conditions.
• Places where water is not sanitized provides the
  perfect environment for Typhoid Fever.

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• Age group Typhoid fever may occur at any age
  but it is considered to be a disease mainly of
  children and young adults. In endemic areas, the
  highest attack rate occurs in children aged 8-13
  years. In a recent study from slums of Delhi, it
  was found that contrary to popular belief, the
  disease affects even children aged 1-5 years

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• Gender and race Typhoid fever cases are
  more commonly seen in males than in females. On
  the contrary, females have a special predilection
  to become chronic carriers.
• Occupation Certain categories of persons
  handling the infective material and live cultures
  of S. typhi are at increased risk of acquiring
  infection.
• Socio-economic factors It is a disease of
  poverty as it is often associated with inadequate
  sanitation facilities and unsafe water supplies.

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• Environmental factors Though the cases are
  observed through out the year, the peak
  incidence of typhoid fever is reported during
  summer. This period coincides with July -
  September rainy season and a substantial increase
  in fly population.
• Social factors pollution of drinking water
  supplies, open air defecation, and urination, low
  standards of food and personal hygiene, and
  health ignorance.

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• Nutritional status Malnutrition may enhance the
  susceptibility to typhoid fever by altering the
  intestinal flora or. other host defences.
• Incubation period Usually 10-14 days but it may
  be as short as 3 days or as long as 21 days
  depending upon the dose of the inoculums.
• Reservoir of infection Man is the only known
  reservoir of infection - cases or carriers
• Period of communicability A case is infectious
  as long as the bacilli appear in stool or urine.

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Risky groups

• Children and young adults in endemic areas.
• Contacts of chronic carriers.
• Microbiology technicians.
• Food handlers.
• Travelers and military personnel

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Typhoid carriers

• About 15 of people who are infected with S.
  typhi become asymptomatic chronic carriers.
• The carrier state may follow acute or mild
  illness or subclinical infection.
• The incidence of chronic carriage is higher among
  women and persons with biliary tract
  abnormalities.

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• Antibiotic use and antibiotic resistance may also
  affect the propensity to become a chronic
  carrier.
• A chronic urinary carrier state occurs in
  individuals with schistosome infection.
• Carriers who handle food without observing proper
  hygiene can transmit infection to others.

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Transmission

• Typhoid is spread by the faecal-oral route.
  Occasionally transmission may be direct, but
  usually it occurs following the ingestion of
  contaminated water or food.
• In developing countries with contaminated water
  supplies and primitive sewage disposal systems,
  water is the most likely vehicle of transmission.

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• Epidemics originating from water
  contamination are particularly explosive.
• Because
• a water source may serve a large population.
• Water dilutes gastric acid which would otherwise
  inactivate pathogenic agents.
• Water and other beverages remain in the stomach
  only very briefly.

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• In more developed countries, with good
  sanitation, typhoid transmission is more likely
  to be associated with food contamination..

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• To summarize
• Modes of transmission
• Water contaminated with fecal materials.
• Contaminated food.
• Food handlers.
• Reservoir
• Only human (cases carriers)

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Communicability

• Typhoid is communicable as long as S. typhi
  organisms are excreted, usually from the first
  week and throughout convalescence.
• About 10 of untreated typhoid fever patients
  will excrete bacteria for 3 month after onset of
  symptoms.

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• Carriers
• may be temporary or chronic.
• Temporary (convalescent or incubatory) carriers
  usually excrete bacilli up to 6-8 weeks.
• Chronic carriers By the end of one year, 3-4
  per cent of cases continue to excrete typhoid
  bacilli.

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Prevention and control

• Basic sanitary and hygienic measures
• Purifying water supplies.
• Improving water delivery and sewage control.
• Construction and use of latrines.
• Boiling water
• Supervision of foodhanders.

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Vaccines

• Three vaccines to typhoid fever
• Killed whole bacteria with side effects.
• 2. Capsular material (Vi antigen) that is safer
  and more effective.
• 3. Live oral vaccine, attenuated S. typhi strain
  (Ty21a).
• Oral vaccines are still being developed to
  distribute in developing countries. Ty21a is
  also being used to carry foreign antigens from
  Shigella and V. cholerae.

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Vaccine Name How given Number of doses necessary Time between doses Total time needed to set aside for vaccination Minimum age for vaccination Booster needed every...
Ty21a (Vivotif Berna, Swiss Serum and Vaccine Institute) ------------ 1 capsule by mouth 4 2 days 2 weeks 6 years 5 years
ViCPS (Typhim Vi, Pasteur Merieux) Injection 1 N/A 2 weeks 2 years 2 years
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• Indication of vaccination
• Travellers to endemic areas.
• People in refugee camps.
• Microbiologists.
• Treatment
• Antibiotics Ciprofloxacin, pefloxacin
  cephalosporins

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• If you know you are traveling to an at risk
  location

• Make sure all food is
• thoughoughly cooked.

• Avoid Ice
• Drink Only Bottled Water

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INTERNET REFERENCES

• www.worldwidevaccines.com
• www.health.gov
• www.rush.edu/worldbook/medical
• www.cdc.gov
• www.nlm.nih.gov
• www.who.int

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Thank you